1. Limited Copyright Waiver
A portion of the disclosure of this patent document contains computer code listings to which the claim of copyright protection is made. The copyright owner has no objection to the facsimile reproduction by any person of the patent document or the patent disclosure, as it appears in the U.S. Patent and Trademark Office patent file or records, but reserves all other rights whatsoever.
2. Field of the Invention
The present invention relates generally to data processing networks, and more particularly to data storage in a data processing network. In particular, the invention relates to using a virus checker in one file server to check for viruses in another file server.
3. Description of Related Art
A computer virus is an intrusive program that infects computer files by inserting in those files copies of itself. When a file containing a virus is executed, the virus may replicate and infect other files, and cause damaging side effects.
As data networks become more open to permit a multiplicity of diverse users to share access to files, the networks are subjected to an increasing threat from viruses. The threat has been addressed by restricting the origin of files to trusted sources, and by using virus checker software to scan the files before the files are executed.
Virus checking software has been installed in a variety of locations within a data network. Users are familiar with virus checking software that runs as a background task on personal computers and workstations. This virus checking software has the disadvantage that it may be disabled or in need of updating to recognize new viruses.
Due to the relative difficulty of maintaining virus checking software on workstations in a network, the virus checkers have been installed in proxy servers and file servers in the network. A proxy server can function as a gatekeeper or filter for files received or transmitted by a group of workstations. A proxy server having a virus checker is an effective means for virus protection for services, such as electronic mail, that are insensitive to transmission delay due to the time that the virus checker needs for scanning the files received or transmitted. The scanning time, however, is relatively long compared to the time for data access in a file server. Therefore, it is often expedient to forego virus checking when accessing a file in a file server. This approach demands that any file contained in the file server must have been scanned for possible viruses before reading from the file. The file server, for example, contains a virus checker utility that scans for viruses. When a user closes a file after any write access to the file, the file is scanned for possible viruses that may have been introduced during the user's write access, before any other user is permitted to open the file. If the virus checker in the file server detects a virus in a file, the file remains locked by the operating system of the file server until the infected file is deleted or disinfected.
There are several difficulties with incorporating a conventional virus checker program into a file server. Conventional virus checkers are written to be loaded and linked with a conventional operating system, such as UNIX or Windows NT. If the file server does not use a conventional operating system, then there will be considerable effort to port the virus checker into the operating system of the file server. In such a case, the provider of the virus checker program may not offer technical assistance or support for the porting effort or maintenance of the virus checker in the environment of the unconventional operating system. In any case, the supplier of the conventional virus checker may demand a license or royalty payment for use of the virus checker program on each file server.